1. Field of the Invention
The invention is directed to the interpretation of ECG characteristics in determining the presence of arrhythmia or any other abnormal ECG presentation (including ST segment deviation), a personalized system to improve user feedback, and automated treatment with the delivery of medication.
2. Description of Related Art
Coronary Artery Disease (CAD) is a condition in which the coronary arteries (the blood vessels which supply the myocardium with oxygenated blood) accumulate plaque, and become less effective in delivering oxygenated blood to the heart. CAD is the most common cause of death worldwide. CAD causes periods of myocardial ischemia, in which the heart's oxygen demand is greater than the supply delivered to it. Prolonged periods of myocardial ischemia lead to necrosis of cardiac cells, resulting in myocardial infarction (MI), commonly known as a heart attack. Acute silent myocardial ischemia is an episodic condition in which blood flow to the heart is restricted, causing a deficiency in oxygen supply to the myocardial tissue and potentially leading to myocardial infarction without demonstrating any symptoms. Whereas non silent myocardial ischemia presents with angina pectoris (a tight pain in the chest) that makes the patient aware of the condition, silent ischemia provides no indication for the victim to obtain immediate treatment. Further, angina pectoris is not a reliable indicator of myocardial ischemia, as patients have varying thresholds for what they consider to be painful sensations of angina. Additionally, the sensations of angina pectoris have been proven to start minutes after myocardial ischemia has started, not be present in many cases of myocardial ischemia, and end significantly before and episode of myocardial ischemia ends.
Almost all patients who experience myocardial ischemia accompanied by angina pectoris also experience silent episodes of myocardial ischemia. Furthermore, there are many patients who experience exclusively silent episodes of myocardial ischemia. The American Heart Association estimates that between 3 and 4 million Americans experience episodes of silent ischemia. Risk factors for silent ischemia include previous myocardial infarctions, coronary artery disease, diabetes, hypertension, smoking, obesity, and existing cardiomyopathy. Cardiomyopathy due to repeated episodes of silent ischemia is one of the most common causes of heart failure in the US. In addition to being a precursor to myocardial infarction, active ischemia is a common underlying cause of ventricular arrhythmia and sudden cardiac death. Additionally, another arrhythmia known as atrial fibrillation can also present without symptoms and is a severe public health burden, as it is a major risk factor for Cerbrovascular Accidents, also known as strokes.
Silent Ischemia can be accurately diagnosed by electrocardiogram, most specifically via transient ST segment changes, T wave inversions, and an increase in heart rate. ST segment depression is the most reliable electrophysiological indicator of acute myocardial ischemia. Nitrates, beta blockers, and calcium channel blockers dilate the coronary arteries and contribute to balancing the heart's oxygen supply and demand. They are the common pharmacological treatment options for ischemia. Nitrates can be administered sublingually by the patient, but is only realistic when indicative symptoms are present. Long-term transdermal nitrate patches can be used prophylactically, but are inevitably subject to the body building a tolerance from extended periods of administration, and must not be worn more than approximately 50 percent of the time. Furthermore, due to the longer time of onset via this route (30-60 minutes) this route of delivery cannot treat an acute onset. Daily beta blocker and calcium channel blocker pills can also prevent or relieve ischemia, but bear the burden of daily side effects that often cause patients to stop taking them.
Thus, there exists a deficiency in the common treatment methods, insofar as the patient can only treat himself/herself during myocardial ischemic episodes in which he feels the sensations of angina pectoris, but not when the attacks are silent. Further deficiencies in the current treatment methods are the necessity to remove a nitrate patch for a substantial portion of time, to minimize nitrate tolerance, thus leaving the patient vulnerable to ischemia attacks during those periods. There exists no system for automated delivery of treatment for myocardial ischemia based on detection of the indicative physiological changes.